Review: Small treatment effect of disodium cromoglycate in childhood asthma is tempered by methodologic flaws and publication biasPDF
ACP J Club. 2001 Jul-Aug;135:24. doi:10.7326/ACPJC-2001-135-1-024
Tasche MJ, Uijen JH, Bernsen RM, de Jongste JC, van der Wouden JC. Inhaled disodium cromoglycate (DSCG) as maintenance therapy in children with asthma: a systematic review. Thorax. 2000 Nov;55:913-20. [PubMed ID: 11050259]
In children with asthma, how effective is inhaled disodium cromoglycate (DSCG)?
Studies were identified by searching MEDLINE, EMBASE/Excerpta Medica, the Cochrane Controlled Trials Register, and the database of the manufacturers of DSCG with the terms asthma, sodium cromoglycate, and clinical trial. Bibliographies of relevant studies were reviewed.
English-language studies were selected if they were randomized, double-blind, placebo-controlled trials of inhaled DSCG in the maintenance treatment of asthma in children up to 18 years of age. Studies of exercise-induced asthma were excluded.
Data were extracted on methodologic quality, setting, design, DSCG dose and method of administration, patient characteristics, duration of intervention, outcomes, and adverse effects. Symptom scores were calculated separately for wheeze and cough. Pooled estimates of the treatment effect were calculated by using random-effects models for absolute and relative effects.
24 trials were included, and patient numbers ranged from 9 to 218. All children had moderate-to-severe asthma, and the median duration of intervention was 4 weeks. Study results favored DSCG in 16 trials, were partially positive in 3, and were equivalent in 5. Heterogeneity was present among the trials. The absolute treatment effects for cough and wheeze on a 0-to-3 scale were statistically significant in favor of DSCG (95% CI 0.11 to 0.26 and CI 0.13 to 0.26, respectively). The relative improvement in means (the difference in mean score divided by the placebo score) for cough and wheeze was also significant (CI for the relative improvement in mean 0.16 to 0.37 and CI 0.19 to 0.36, respectively). Funnel plots showed significant publication bias by the absence of small, negative trials (P = 0.095 for cough and P = 0.01 for wheeze).
In children with asthma, a meta-analysis of 24 randomized controlled trials shows a small treatment effect of inhaled disodium cromoglycate. The results are tempered by mediocre methodologic quality of the trials, heterogeneity, and publication bias.
Source of funding: No external funding.
For correspondence: Dr. J.C. van der Wouden, Department of General Practice, FF325, Erasmus University and University Hospital/Sophia Children's Hospital, 3000 DR Rotterdam, The Netherlands. FAX 31-10-408-9491.
The systematic review by Tasche and colleagues had a well-focused question, and the criteria used to select articles for inclusion were appropriate. The authors point out that important relevant studies may have been missed (examination of the funnel plot) but that their exclusion would further dilute, not enhance, the effect of DSCG. Acknowledging that the methodologic quality of the trials was mediocre, the authors statistically pooled the results and showed that the tolerance interval included zero. They concluded that it is no longer justified to use DSCG as a first-line prophylactic agent in childhood asthma.
This meta-analysis together with the results of the following studies (1, 2) may encourage many to use inhaled corticosteroids (ICSs) as first- line therapy. One trial showed that in children with mild-to-moderate asthma, inhaled budesonide improved airway responsiveness and provided better control of asthma than did placebo or nedocromil. Its side effects were limited to a small, transient reduction in growth velocity (1). Another trial concluded that children with asthma who received long-term treatment with budesonide attained normal adult height (2).
Because asthma is the most common chronic disease in childhood, the clinical application of this evidence is important. If the concerns of ICSs on growth are no longer an issue, some may think that ICSs are as safe as other anti-inflammatory agents. However, the long-term effects of steroids on the developing immune system are still unknown. Until long-term marketing surveillance establishes the safety of ICSs, clinicians must continue to weigh the risks and benefits when choosing ICSs over DSCG.
Lynnette J. Mazur, MD, MPH
University of Texas
Houston, Texas, USA